Intermittent drive mechanism



Oct. 12, 1965 YOSHIO MURAI 3,211,012

INTERMITTENT DRIVE MECHANISM Original Filed Jan. 2, 1962 United States Patent 3,211,012 INTERMITTENT DRIVE MECHANISM Yoshio Murai, Tsurumi-ku, Yokohama-shi, Japan, assignor to Kabushiki Kaisha Hattori Tokeiten, Tokyoto, Japan, a joint-stock company of Japan Original application Jan. 2, 1962, Ser. No. 163,550. Divided and this application June 27, 1963, Ser. No. 297,481

Claims priority, application Japan, Oct. 24, 1961, 36/38,067 2 Claims. (Cl. 7488) This application is a division of my prior-filed application S.N. 163,550 filed January 2, 1962, entitled Electronic Timepieces Utilizing Transistors, now abandoned, and the present invention relates to an intermittent drive mechanism for accomplishing a change of motion from oscillation to intermittent rotary motion in either direction. More particularly, the invention relates to such a drive mechanism for incorporation in a timepiece of the balance wheel type in which the balance wheel is electromagnetically driven. For example, a timepiece such as disclosed in such prior filed application.

It is, therefore, an object of the present invention to provide an intermittent drive mechanism which will effect the timing movements of the timepiece and in which there is incorporated structure lending itself to a compact size relationship of parts. It is a further and more specific object to provide an intermittent drive mechanism for timepieces which includes an oscillatory balance wheel, a balance swing pin fixed to said wheel to move therewith, two identical multi-star wheels having their teeth intermeshing but spaced to prevent contact therebetween, a shaft for each star wheel and two intermeshing timing gears of unity gear ratio, one fixed to each shaft so as to move in unison with said star wheels whereby engagement of the balance pins with the star wheel depending on direction of movement with the pin intermittently turns the timing gears.

It is a further and more specific object to shape the teeth of the star wheels so that the surfaces to be engaged are contacted by the balance swing pin and in the form of circular arcs.

Further and more specific objects will be apparent from the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a diagrammatic end elevation view of an intermittent drive mechanism of a timepiece in accordance with the invention.

FIG. 2 through FIG. 7 are diagrammatic plan views showing successive positions of the drive mechanism during movement of the balance swing pin through the oscillation path in both directions of movement.

FIG. 8 is a diagrammatic view illustrating relationship of the arcuate surface tooth profile of the star wheels of the invention with respect to the balance swing pin.

In general and for the purpose of illustration, the timepiece includes a balance wheel assembly 5 which is rotatably supported so as to oscillate back and forth. This assembly has two permanent magnets 6 fixed to a portion thereof and two balance weights 7 fastened to another portion thereof. A coil 8 is supported between and not mechanically touching the two magnets 6. The balance wheel 5 receives driving impulses from the coil so as to oscillate as is known in the art. A balance swing pin 2 is fixed to the balance wheel to impart reciprocating percussion turning movement to two star wheels 3a and 3b of the intermittent drive mechanism. The drive mechanism includes the intermeshed gears 4a and 4b having a mutual gear ratio of 1 which are fixed to and rotate with said star wheels 3a and 3b, respectively.

A shaft carrying a worm 15 transmits power from the intermittent drive mechanism to the wheel train of the timepiece, not shown, via worm wheel 16 fixed to a second hand shaft which is in mesh with the worm 15.

The operation of the reverse escapement mechanism according to the present invention will now be described with reference to FIGS. 2 to 6. It will first be assumed that, when the swing pin 2 undergoes a half oscillation from a point B in the arrow direction and passes the neutral point A, the two six-point star wheels 3a and 3b are in the relative positions indicated in FIG. 2. Then, since the six-point star wheel 36 is positioned outside of the path of the swing pin 2, the swing pin passes the neutral point A without contacting the six-point star Wheel 36 and swings beyond the point A by an angle a.

If, at this time, an external driving force acts on the balance wheel, the balance wheel swing pin, without weakening its oscillation, engages and rotates the star wheel 3a, see FIG. 3, through an angle 3 from the point A as indicated in FIG. 4 to a position outside of the path of movement of the swing pin 2 and thereafter completes the remainder of its half oscillation to a point C.

By the above-described motions, the star wheel 3a which has been caused to turn through an angle (;3a) by the swing pin 2 as shown in FIG. 4 causes the worm 15 fixed to the same shaft as the star wheel 3a to turn through (fi-a), thereby becoming a power source for the wheel train of the timepiece. At the same time, the gear 4a meshed with gear 4b, which is also fixed to the same said shaft, is also rotated by (B-a), and the other star wheel 3b fixed to the gear 4b is rotated in the arrow direction, whereby the various parts are placed in the relative positions indicated in FIG. 4. That is, the swing pin 2 causes the star wheel 3a to rotate in the arrow direction shown and, at the same time, causes the other star wheel 3b to undergo intermittent motion in the arrow direction shown, simultaneously completing the preparation for subsequent percussion.

Next, the swing pin 2 undergoes a half oscillation from the point C in the arrow direction as shown in FIG. 5 and, without contacting the star wheel 3a, passes the neutral point A. Then, the swing pin 2 is subjected to an external driving force, and in exactly the same manner, see FIGS. 6 and 7, it causes the star wheel 3b to rotate and causes the worm 15, through the gears 4a and 4b, to rotate, at the same time preparing the other star wheel 3a for the subsequent reverse percussion.

When six-point star wheels are used for the abovedescribed star Wheels, intermittent rotation is obtained when, by reason of the mechanism, the angle at is made to be 30 degrees. In some cases, however, depending on the position of the balance swing pin, the impact angle of the external driving force on the balance wheel, the impact duration angle, and other factors, the use of star wheels other than six-point star wheels may be preferable.

It is both advantageous and safe to design the tooth profile of a star-wheel type, reverse-escapement mechanism to be of such a configuration that the operational relation between the swing pin 2 and the two star wheels is unaffected by positional deviations caused by external impact of a certain degree, thereby maintaining normal operation, and that the positions are restored. That is, it is a unique feature of the invention that the operational surfaces of the aforesaid star wheels 3a and 3b with respect to the swing pin 2 are made in the form of circular arcs.

In the case of a mechanism of this type which undergoes alternating motion and has star wheels with straightline tooth profile, no problem will occur if the normal operational positions are constantly maintained. However, if an external force such as impact is imparted to the mechanism, the star wheels sometimes may rotate in reverse direction, and, as an undesirable result, the swing pin will strike against the tip of a tooth and stop the balance wheel or move the star wheel in the opposite direction.

By making the surfaces of the star Wheels 3a and 3b which operate in contact With the swing pin 2 in the form of circular arcs a, see FIG. 8, the extreme tip of the tooth is caused to be positioned outside of the path of motion of the swing pin 2 even when the mechanism is subjected to an external force, and the star wheels 3a and 3b are rotated in reverse direction as indicated in FIG. 8. Since the swing pin 2 contacts the star Wheel on the arc surface a, it does not create any abnormal action and, moreover, compulsorily corrects the star wheels to their correct, normal positions that is, moves the same through distance t, see FIG. 8.

A tooth profile of the foregoing description has practical effectiveness in enabling the timekeeping operation, at the time of positional deviation in a star-wheel type, reverse-escapement mechanism, to be corrected automatically to the normal operation without being disturbed or suppressed.

The mechanism of the present invention, since it enables the tangential force of the balance swing pin to be taken off in the same plane, has high transmission efficiency and short contact time. Accordingly, the balance wheel mechanism does not lose its isochronism and, moreover, can be fabricated in a simple manner.

Although this invention has been described with respect to a particular embodiment thereof, it is not to be so limited as changes and modifications may be made therein which are within the full intended scope of the invention, as defined by the appended claims.

What is claimed is:

1. A timepiece intermittent drive mechanism for converting oscillatory into intermittent unidirectional rotary motion comprising an oscillatory balance wheel, a balance swing pin fixed to said balance wheel, two identical co-planar star wheels having teeth spaced to prevent driving contact therebetween while allowing each tooth on one wheel to pass between adjacent teeth on the other wheel and each tooth having sufiicient projection to be engaged by said swing pin, a shaft for each star wheel and tWo intermeshing timing gears of unity gear ratio, one fixed on each shaft so as to move in unison with said star wheels and the spaces of the teeth of such star wheels relative to the path of motion of said swing pin ensuring that said swing pin impart percussion to the tooth of one star wheel and at the same time, causes the tooth of the other star wheel to be positioned for subsequent percussion thereby converting oscillatory motion of said pin into unidirectional rotation of said gears.

2. A timepiece intermittent drive mechanism as claimed in claim 1 and said star wheels having surfaces that are to be contacted by said swing pin in the form of such circular arcs that are tangent to the circle described by the tooth engaging surface of said pin at the point of release of said pin from said surfaces in either direction of movement of the pin and said surfaces.

References Cited by the Examiner UNITED STATES PATENTS 1,213,716 1/17 Wentworth 58ll7 2,877,654 3/59 Biemiller et al. 7488 3,143,848 8/64 Biemiller et a] 7488 X BROUGHTON G. DURHAM, Primary Examiner. 

1. A TIMEPIECE INTERMITTENT DRIVE MECHANISM FOR CONVERTING OSCILLATORY INTO INTERMITTENT UNIDIRECTIONAL ROTARY MOTION COMPRISING AN OSCILLATORY BALANCE WHEEL, A BALANCE SWING PIN FIXED TO SAID BALANCE WHEEL, TWO IDENTICAL CO-PLANAR STAR WHEELS HAVING TEETH SPACED TO PREVENT DRIVING CONTACT THEREBETWEEN WHILE ALLOWING EACH TOOTH ON ONE WHEEL TO PASS BETWEEN ADJACENT TEETH ON THE OTHER WHEEL AND EACH TOOTH HAVING SUFFICIENT PROJECTION TO BE ENGAGED BY SAID SWING PIN, A SHAFT FOR EACH STAR WHEEL AND TWO INTERMESHING TIMING GEARS OF UNITARY GEAR RATIO, 